An image forming apparatus including an image forming section; an upper unit located over the image forming section with a space therebetween and slidable in a direction of from the front side to the rear side of the apparatus and the opposite direction; a sheet discharger configured to discharge a sheet bearing an image in the first or opposite direction; a sheet stacker receiving the sheet from the sheet discharger; a support arranged outside of both side ends of the sheet stacker in the first direction and slidably supporting the upper unit; and at least one of a release preventing member for preventing releasing of the upper unit from the support, and a covering member movable from a first position to a second position in conjunction with sliding of the upper unit and covering an opening formed at an end portion of the support when acquiring the first position.
